Dynamic reference method and system for use with surgical procedures

ABSTRACT

A substrate configured for placement on an internal organ or tissue is provided. In certain embodiments, the substrate conforms to and moves with the internal organ or tissue. Three or more sensor elements are integrated on the substrate. In one implementation, the substrate and associated sensor elements provide dynamic referencing of the internal organ or tissue after registration of the sensor data with images and/or volumetric representations of the internal organ or tissue.

BACKGROUND

The present technique relates generally to invasive procedures, such assurgical procedures. In particular, the present technique relates toimage-guided surgery employing various radiological modalities.

As medical imaging technologies have matured, it has become possible tocombine the use of medical imaging techniques with the performance ofinvasive procedures. For example, invasive procedures, such as certainsurgical procedures, may benefit from the use of imaging techniques thatallow a clinician to visualize the internal or obscured structures inthe surgical area while the procedure is being performed. In this way,the clinician may perform the desired surgical procedure with a greaterchance of success and without unnecessary tissue damage.

In practice, such image-guided surgical techniques typically employ atracking frame of reference device placed proximate to the anatomy ofinterest. The reference device moves with the patient to provideaccurate and consistent tracking of the anatomy of interest. Typically,the reference device needs to be rigidly secured to the anatomy ofinterest. As a result, the reference device is generally attached tohard bone near the anatomy of interest. As a result, such image-guidedsurgical techniques are generally limited to regions in the body boundedby bony anatomy, such as cranial neurosurgery, spine, orthopedic, andsinus procedures.

While such techniques are useful, clearly there are other areas of thebody that are not bounded by bony structures and that might also benefitfrom such image-guided techniques. However, regions of the body that arenot bounded by such bony structures, such as cardiac and abdominalregions, currently cannot benefit from such image-guided techniques dueto the inability to affix a reference device proximate to the anatomy ofinterest. Further, many internal organs that might benefit fromimage-guided surgical techniques can move, such as due to respiration,gravity, and so forth, and therefore, present additional interventionalchallenges. In addition, even in regions of the anatomy where there isproximate bone, it may not be desirable to attach a reference device tothe bone. Therefore, it is desirable to provide a reference techniquefor image-guided surgical procedures that does not require a referencedevice affixed to skeletal structures.

BRIEF DESCRIPTION

The present technique is generally directed to the dynamic referencingof an internal organ or tissue in an image-guided invasive procedure. Inone implementation, a substrate having three or more sensor elements isprovided. In such an embodiment, the substrate is placed on an internalorgan, such as during a surgical open or laparoscopic procedure. Signalsor fields generated by the sensor elements, such as electromagneticsignals or fields, may be used to determine the positions of the sensorelements. The positions of the sensor elements may then be registeredwith a set of image based data which may or may not include image datarepresentative of the sensor elements. In one embodiment, theregistration occurs automatically. Once the signals generated by thesensor elements is registered with the images or volumetricrepresentations of the internal organ, the position and orientationinformation derived from the sensor elements may be used to modify oradjust the visual representation of the internal organ to reflect motionor deformation of the organ. The modified or adjusted visualrepresentation may then be used to allow a surgeon or other clinician toperform an image-guided invasive procedure based on images reflectingthe current position and shape of the internal organ.

In accordance with one aspect of the present technique, a surgicalreference system is provided. The surgical reference system includes asubstrate configured for placement on an internal organ or tissue suchthat the substrate conforms to and moves with the internal organ ortissue. Three or more sensor elements are integrated on the substrate.

In accordance with a further aspect of the present technique, a methodfor tracking dynamic motion of an organ is provided. The method includesthe act of generating a first set of position data for three or moresensor components integrated on a substrate placed on an internal organ.The first set of position data is based on signals or fields generatedby the sensor components. A second set of position data is generated forthe three or more sensor components based on an identification of thethree or more sensor components in one or more radiological images orvolumetric representations of the internal organ. Corresponding sensorcomponents are identified in the first set of position data and thesecond set of position data. The first set of position data isregistered with the one or more radiological images or volumetricrepresentations based on the identification of corresponding sensorcomponents in the first set of position data and the second set ofposition data.

In accordance with an additional aspect of the present technique, amethod for tracking dynamic motion of an organ is provided. The methodincludes the act of generating position and orientation data for one ormore sensor components provided on a substrate placed on an internalorgan. The position and orientation data is based on signals or fieldsgenerated by the sensor components. A shape model of the substrate isgenerated based on the position and orientation data. In addition, aregion of interest in one or more radiological images or volumetricrepresentations is segmented. The region of interest comprises at leastone of the internal organ, a portion of the internal organ, or a regionproximate or connected to the internal organ. A shape model of theregion of interest is generated based on the segmentation. The shapemodel of the substrate and the shape model of the region of interest areregistered.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 depicts a piece of surgical gauze including sensor components, inaccordance with an exemplary embodiment of the present technique;

FIG. 2 depicts a piece of surgical gauze including sensor componentsplaced on an organ, in accordance with an exemplary embodiment of thepresent technique;

FIG. 3 depicts exemplary components of an imaging system and a positiondetermining system, in accordance with an exemplary embodiment of thepresent technique;

FIG. 4 depicts exemplary components of a computed tomography orthree-dimensional fluoroscopy imaging system and a position determiningsystem, in accordance with an exemplary embodiment of the presenttechnique;

FIG. 5 depicts exemplary acts for using a position determining system,in accordance with an exemplary embodiment of the present technique; and

FIG. 6 depicts exemplary acts for using a position determining system,in accordance with a further exemplary embodiment of the presenttechnique.

DETAILED DESCRIPTION

The present technique is directed to dynamic referencing of internalorgans for image-guided surgical procedures. In particular, the presenttechnique utilizes a conformable member or substrate, such as gauze or abiocompatible plastic, configured with one or more tracking devices. Theconformable substrate is configured for placement on or near an internalorgan of interest such that movement of the organ can be tracked inconjunction with acquired images or image data. In particular, in anexemplary embodiment, the movement of the tracking devices isautomatically registered with the image data, without the use ofanatomical or fiducial markers. In this manner, an image-guided surgicalprocedure may be performed using the dynamic reference informationacquired using the substrate. Because the substrate can be associatedwith the anatomy of interest without being affixed to bone, the presenttechnique may be suitable for use with percutaneous procedures performedon internal organs that may move or be moved and which are not close toa suitable skeletal anchor. Examples of such organs include, but are notlimited to the liver, lungs, kidneys, pancreas, bladder, and so forth.

For example, referring to FIG. 1, a biocompatible substrate 10 isdepicted that is suitable for placement near or on an organ of interest.In an exemplary embodiment, the substrate 10 is a conformable piece ofsurgical gauze 20 which may be of any suitable dimensions or shape. Thesubstrate 10 is provided with three or more sensor elements 16 that, inan exemplary embodiment, may be used to acquire position informationrelating to the substrate 10. Indeed, in certain exemplary embodimentsit may be desirable to include more than three sensor elements 16because the number of sensor elements 16 will generally provide morepoints defining the surface of an organ on which the substrate isplaced. In other words, the number of sensor elements 16 provided on thesubstrate 10 is generally proportional to the level of surface orconformational detail provided by the substrate 10 when placed on anorgan.

In the depicted embodiment, a conductive element 18 is also providedwhich may be suitable for providing power to the sensor elements 16 inimplementations in which the sensor elements are powered. In oneimplementation, where the substrate 10 is a piece of surgical gauze, theconductive element 18 may be run through the blue tail commonly found onsurgical gauze. In such embodiments, the blue tail, may be impregnatedwith barium so that the gauze is easily located using X-ray basedimaging techniques.

The exemplary substrate 10 is depicted placed on an internal organ 24(here depicted as a liver) in FIG. 2. The substrate 10 may be placed onthe internal organ 24 as part of an open surgical procedure in which theinternal organ 24 is exposed. Alternatively, the substrate 10 may beplaced on the internal organ 24 using laparoscopic surgical techniquesutilizing a small incision. For example, in such laparscopicimplementations, the substrate 10 may be introduced through a smallincision in a rolled or folded form, maneuvered to the internal organsite, and unrolled or unfolded on or near the internal organ 24 usinglaparoscopic techniques. For example, laparoscopic delivery may beaccomplished using a suitable catheter for delivery of a piece of gauze20.

In an exemplary embodiment, the substrate 10, regardless of how it isplaced on or near the internal organ 24, conforms to the shape of theinternal organ 24 at the location where the substrate 10 overlays theinternal organ 24. For example, the substrate 10, in one embodiment, maybe a piece of surgical gauze 20 that adheres to the internal organ 24due to the surface tension of fluids on the surface of the internalorgan 24. Such adhesion may be enhanced or improved by the addition ofsaline or other suitable fluids to the surface of the internal organ 24.In embodiments where the substrate 10 is conformable, such as where thesubstrate 10 is a piece of gauze 20, the shape assumed by theconformable substrate 10 generally corresponds to the correspondingsurface of the internal organ at that location. Further, in such animplementation, the conformable substrate 10 may be placed on an area ofthe internal organ 24 having sufficient curvature such that the area maybe uniquely identified by the sensor elements 16, as discussed below.

In exemplary implementations in which the internal organ 24 (such as thedepicted liver) moves essentially as a rigid body during respiration,the substrate 10 placed on or near the internal organ 24 will move withthe internal organ 24. Further, to the extent that the substrate 10conforms to the internal organ 24, the substrate 10 will reflectconformational changes in the internal organ 24, i.e., if the internalorgan changes shape, the substrate 10 will conform to the internal organ24 and will, therefore, deform to the new shape of the internal organ24. Because the substrate 10 will move with and conform to the internalorgan 24, the substrate 10 can act as a dynamic reference with regard tothe internal organ 24. As a result, a surgical procedure, such assurgical removal (such as with a tracked needle 30) of a lesion 26 usinglaparoscopic or open techniques, can be performed using image-guidednavigation using position or motion information obtained using thesensor elements 16 integrated on the substrate 10.

Typically, the sensor elements 16 are not provided in a linear orsymmetric arrangement, i.e., the sensor elements 16 do not form a singleline, such that the respective sensor elements 16 can be distinguishedfrom one another based upon their known spatial relationships. Forexample, in the exemplary depicted embodiments of FIGS. 1 and 2, thesensor elements 16 are provided in a 3×5 array such that the totality ofinformation received from the sensor elements 16 can be used todistinguish the respective sensor elements 16 from one another.

In one embodiment, the sensor elements 16 are provided aselectromagnetic (EM) microsensors that are integrated into or securelyattached to the substrate 10. Such EM microsensors may be provided aseither hollow or solid sensor coils which generate EM fields. Exemplarysolid EM coils may be about 0.75 mm in diameter (or greater) and about 2mm long (or greater). Likewise, exemplary hollow EM coils may be about 2mm in diameter (or greater) and about 2 mm long (or greater). Such solidor hollow EM coils can provide a spatial tracking accuracy having lessthan about 1 mm root mean square (RMS) error. Further each sensor coilcan be tracked in position with this accuracy over a volume sufficientfor the image-guided procedures described herein, i.e., within the fieldof view of a medical imaging system.

In implementations employing such EM coils, each EM sensor coil canprovide information regarding the orientation of the respective coil intwo directions. In one embodiment, however, a single coil cannot providesufficient information to determine the roll of the respective coilsince the coils are axisymmetric. Therefore, each coil, in such anembodiment, has five degrees of freedom. If at least two such coils arecombined into or integrated onto a device, such as the substrate 10, sothat the coils have a known and fixed relationship to one another, thensix degrees of freedom (x, y, z, roll, pitch, yaw) can be determinedfrom the aggregate or combined information obtained form the two or morecoils. In this way, the EM fields generated by the EM coils may be usedto determine the position and orientation of the substrate 10 upon whichthey are integrated. For example, in the embodiment depicted in FIGS. 1and 2, the sensor elements 16 (which are presumed to be EM coils in thisexample) that are fixed on the substrate 10 allow the position,orientation, and conformation (i.e., shape) of the substrate 10 to bedetermined based upon the EM fields generated by the EM coils.

As described above, a substrate 10 may be used accordance with thepresent technique to allow image-guided invasive procedures. As will beappreciated, any imaging modality suitable for use in an image-guidedsurgical procedure may be employed in the present technique. Examples ofsuch imaging modalities include X-ray based imaging techniques whichutilize the differential attenuation of X-rays to generate images (suchas three-dimensional fluoroscopy, computed tomography (CT),tomosynthesis techniques, and other X-ray based imaging technologies).Other exemplary imaging modalities suitable for image-guided surgicalprocedures may include magnetic resonance imaging (MRI), ultrasound orthermoacoustic imaging techniques, and/or optical imaging techniques.Likewise, nuclear medicine imaging techniques (such as positron emissiontomography (PET) or single positron emission computed tomography(SPECT)) that utilize radiopharmaceuticals may also be suitable imagingtechnologies for performing image-guided surgical procedures. Likewise,combined imaging modality systems, such as PET/CT systems, may also besuitable for performing image-guided surgical procedures as describedherein. Therefore, throughout the present discussion, it should be bornein mind that the present techniques are generally independent of thesystem or modality used to acquire the image data. That is, thetechnique may operate on stored raw, processed or partially processedimage data from any suitable source.

For example, turning now to FIG. 3, an overview of an exemplarygeneralized imaging system 34, which may be representative of variousimaging modalities, is depicted. The generalized imaging system 34typically includes some type of imager 36 which detects signals andconverts the signals to useful data. As described more fully below, theimager 36 may operate in accordance with various physical principles forcreating the image data. In general, however, image data indicative ofregions of interest in a patient 38 are created by the imager 36 in adigital medium for use in image-guided surgical procedures.

The imager 36 may be operated by system control circuitry 40 whichcontrols various aspects of the imager operation and acquisition andprocessing of the image data as well as dynamic reference data acquiredusing the present techniques. In the depicted generalized embodiment,the system control circuitry 40 includes movement and control circuitry42 useful in operating the imager 36. For example, the movement andcontrol circuitry 42 may include radiation source control circuits,timing circuits, circuits for coordinating the relative motion of theimager 36 (such as with regard to a patient support and/or detectorassembly), and so forth. The imager 36, following acquisition of theimage data or signals, may process the signals, such as for conversionto digital values, and forwards the image data to data acquisitioncircuitry 44. For digital systems, the data acquisition circuitry 44 mayperform a wide range of initial processing functions, such as adjustmentof digital dynamic ranges, smoothing or sharpening of data, as well ascompiling of data streams and files, where desired. The data are thentransferred to data processing circuitry 46 where additional processingand analysis are performed. For the various digital imaging systemsavailable, the data processing circuitry 46 may perform substantialreconstruction and/or analyses of data, ordering of data, sharpening,smoothing, feature recognition, and so forth.

In addition to processing the image data, the processing circuitry 46may also receive and process motion or location information related toan anatomical region of interest, such as the depicted internal organ 24and/or lesion 26 which are accessible via an open surgical incision 48or a laparoscopic surgical entry. In the depicted embodiment, asubstrate 10 is placed on the internal organ 24 (here depicted as theliver of the patient 38). The substrate 10, as discussed above, isprovided with numerous (for example, three or more) sensor elements 16(see FIGS. 1 and 2) configured to provide position information. In anexemplary embodiment, the sensor elements 16 are EM coils eachconfigured to generate a distinctive and distinguishable EM field. Incertain embodiments where the sensor elements 16 are powered, the sensorelements 16 may be connected, such as via one or more conductive wires50, to suitable power circuitry 52, such as an electrical power sourceor outlet or a suitable battery. While in the depicted embodiment thepower circuitry 52 is depicted as being separate from the system controlcircuitry 40, in other embodiments the power circuitry 52 may be part ofthe system control circuitry 40.

In the depicted embodiment, the signals or fields generated by thesensor elements 16 are detected by one or more antennas 54. The detectedlocation information is provided to or acquired by receiver circuitry 56which in turn provides the location data to the processing circuitry 46.As discussed in greater detail below, the location data may be used inconjunction with the image data to facilitate an image-guided procedure.In another embodiment, the antennas 54 are used for transmission insteadof detection, i.e., the antennas 54 are transmitters, and generate EMfields which are detected by the sensors elements 16. In eitherembodiment, location information can be determined in sufficient detailto allow the motion and/or configuration of the organ to be tracked.

The processed image data and/or location data may be forward to displaycircuitry 60 for display at a monitor 62 for viewing and analysis. Whileoperations may be performed on the image data prior to viewing, themonitor 62 is at some point useful for viewing reconstructed imagesderived from the image data collected. The images may also be stored inshort or long-term storage devices which may be local to the imagingsystem 34, such as within the system control circuitry 40, or remotefrom the imaging system 34, such as in picture archiving communicationsystems. The image data can also be transferred to remote locations,such as via a network.

For simplicity, certain of the circuitry discussed above, such as themovement and control circuitry 42, the data acquisition circuitry 44,the processing circuitry 46, and the display circuitry 60, are depictedand discussed as being part of the system control circuitry 40. Such adepiction and discussion is for the purpose of illustration only,however, and is intended to merely exemplify one possible arrangement ofthis circuitry in a manner that is readily understandable. Those skilledin the art will readily appreciate that in other embodiments thedepicted circuitry may be provided in different arrangements and/orlocations. For example, certain circuits may be provided in differentprocessor-based systems or workstations or as integral to differentstructures, such as imaging workstations, system control panels, and soforth, which functionally communicate to accomplish the techniquesdescribed herein.

The operation of the imaging system 34 may be controlled by an operatorvia a user interface 52 which may include various user input device,such as a mouse, keyboard, touch screen, and so forth. Such a userinterface may be configured to provide inputs and commands to the systemcontrol circuitry 40, as depicted. Moreover, it should also be notedthat more than a single user interface 52 may be provided. Accordingly,an imaging scanner or station may include an interface which permitsregulation of the parameters involved in the image data acquisitionprocedure, whereas a different user interface may be provided formanipulating, enhancing, and viewing resulting reconstructed images.

To discuss the technique in greater detail, a specific medical imagingmodality based generally upon the overall system architecture outlinedin FIG. 3 is depicted in FIG. 4, which generally represents an X-raybased system 70. It should be noted that, while reference is made inFIG. 4 to an X-ray based system, the present technique also encompassesother imaging modalities, as discussed above, such as MRI, PET, SPECT,ultrasound, and so forth.

In the depicted exemplary embodiment, FIG. 4 illustratesdiagrammatically an X-ray based imaging system 70 for acquiring andprocessing image data. In the illustrated embodiment, imaging system 70is a computed tomography (CT) system or three-dimensional fluoroscopyimaging system designed to acquire X-ray projection data, to reconstructthe projection data into a two or three-dimensional image, and toprocess the image for display and analysis in accordance with thepresent technique. In the embodiment illustrated in FIG. 4, X-ray basedimaging system 70 includes a source of X-ray radiation 72 positionedadjacent to a collimator 74. The X-ray source 72 may be a standard X-raytube or one or more solid-sate X-ray emitters.

In the depicted embodiment, the collimator 74 permits a stream ofradiation 76 to pass into a region in which a subject, such as thepatient 38 is positioned. The stream of radiation 76 may be generallyfan or cone shaped, depending on the configuration of the detector arrayas well as the desired method of data acquisition. A portion of theradiation 78 passes through or around the patient 38 and impacts adetector array, represented generally as reference numeral 80. Detectorelements of the array produce electrical signals that represent theintensity of the incident X-ray beam. The signals generated by thedetector array 80 may be subsequently processed to reconstruct a visualrepresentation (i.e., an image or volumetric representation) of thefeatures within the patient 38. For example, images of the internalorgan 24 may be reconstructed in the depicted embodiment.

A variety of configurations of the detector 80 may be employed inconjunction with the techniques described herein. For example, thedetector 80 may be a multi-row detector, such as a detector having eightor sixteen rows of detector elements, which achieves limitedlongitudinal coverage of the object or patient being scanned. Similarly,the detector 80 may be an area detector, such as a high-resolutionradiographic detector having hundreds of rows of detector elements,which allows positioning of the entire object or organ being imagedwithin the field of view of the system 70. Regardless of theconfiguration, the detector 80 enables acquisition and/or measurement ofthe data used in image reconstruction of the internal organ 24.

The source 72 is controlled by a system controller 84, which furnishesboth power, and control signals for examination procedures. Moreover,the detector 80 is coupled to the system controller 84, which commandsacquisition of the signals generated in the detector 80. The systemcontroller 84 may also execute various signal processing and filtrationfunctions, such as for initial adjustment of dynamic ranges,interleaving of digital image data, and so forth. In general, systemcontroller 84 commands operation of the imaging system 70 to executeexamination protocols and to process acquired data. In the presentcontext, system controller 84 also includes signal processing circuitry,typically based upon a general purpose or application-specific digitalcomputer, associated memory circuitry for storing programs and routinesexecuted by the computer (such as programs and routines for implementingthe present technique), as well as configuration parameters and imagedata, interface circuits, and so forth.

In the embodiment illustrated in FIG. 4, the system controller 84 iscoupled to a linear positioning subsystem 86 and rotational subsystem88. The rotational subsystem 88 enables the X-ray source 72, collimator74 and the detector 80 to be rotated one or multiple turns around thepatient 38. It should be noted that the rotational subsystem 88 mightinclude a gantry or C-arm apparatus. Thus, the system controller 84 maybe utilized to operate the gantry or C-arm. The linear positioningsubsystem 86 typically enables a patient support, such as a table, uponwhich the patient rests, to be displaced linearly. Thus, the patienttable may be linearly moved relative to the gantry or C-arm to generateimages of particular areas of the patient 38.

Additionally, as will be appreciated by those skilled in the art, thesource 72 of radiation may be controlled by an X-ray controller 90disposed within the system controller 84. Particularly, the X-raycontroller 90 may be configured to provide power and timing signals tothe X-ray source 72. A motor controller 92 may also be part of thesystem controller 84 and may be utilized to control the movement of therotational subsystem 88 and the linear positioning subsystem 86.

Further, the system controller 84 is also illustrated as including animage data acquisition system 94. In this exemplary embodiment, thedetector 80 is coupled to the system controller 84, and moreparticularly to the image data acquisition system 94. The image dataacquisition system 94 receives data collected by readout electronics ofthe detector 80. The image data acquisition system 94 typically receivessampled analog signals from the detector 90 and converts the data todigital signals for subsequent processing by processing circuitry 96,which may, for example, be one or more processors of a general orapplication specific computer.

As depicted, the system controller 84 also includes aposition/orientation data acquisition system 100 configured to acquireposition and orientation data from one or more antennas 102. In thedepicted embodiment, the one or more antennas 102 detect signals and/orfields generated by sensor elements 16 on a substrate 10 placed on theinternal organ 24 undergoing imaging. The position/orientation dataacquisition system 100 processes signals acquired from the antennas 102to generate position and/or orientation information about the substrate10 which is representative of the internal organ 24. The position and/ororientation information generated by the position/orientation dataacquisition system 100 may be provided to the processing circuitry 96and/or a memory 98 for subsequent processing.

The processing circuitry 96 is typically coupled to the systemcontroller 84. The data collected by the image data acquisition system94 and/or by the position/orientation data acquisition system 100 may betransmitted to the processing circuitry 96 for subsequent processing andvisual reconstruction. The processing circuitry 96 may include (or maycommunicate with) a memory 98 that can store data processed by theprocessing circuitry 96 or data to be processed by the processingcircuitry 96. It should be understood that any type of computeraccessible memory device capable of storing the desired amount of dataand/or code may be utilized by such an exemplary system 70. Moreover,the memory 98 may include one or more memory devices, such as magneticor optical devices, of similar or different types, which may be localand/or remote to the system 70. The memory 98 may store data, processingparameters, and/or computer programs having one or more routines forperforming the processes described herein.

The processing circuitry 96 may be adapted to control features enabledby the system controller 84, i.e., scanning operations and dataacquisition. For example, the processing circuitry 96 may be configuredto receive commands and scanning parameters from an operator via anoperator interface 106 typically equipped with a keyboard and otherinput devices (not shown). An operator may thereby control the system 70via the input devices. A display 108 coupled to the operator interface106 may be utilized to observe a reconstructed visual representation.Additionally, the reconstructed image may also be printed by a printer110, which may be coupled to the operator interface 106. As will beappreciated, one or more operator interfaces 106 may be linked to thesystem 70 for outputting system parameters, requesting examinations,viewing images, and so forth. In general, displays, printers,workstations, and similar devices supplied within the system may belocal to the data acquisition components, or may be remote from thesecomponents, such as elsewhere within an institution or hospital, or inan entirely different location, linked to the image acquisition systemvia one or more configurable networks, such as the Internet, virtualprivate networks, and so forth.

The processing circuitry 96 may also be coupled to a picture archivingand communications system (PACS) 112. Image data generated or processedby the processing circuitry 96 may be transmitted to and stored at thePACS 112 for subsequent processing or review. It should be noted thatPACS 112 might be coupled to a remote client 114, radiology departmentinformation system (RIS), hospital information system (HIS) or to aninternal or external network, so that others at different locations maygain access to the image data.

The systems and devices described above may be utilized, as describedherein, to provide dynamic referencing for a region of a patientundergoing an invasive procedure, such as a surgical open orlaparoscopic procedure. In an exemplary embodiment, dynamically acquiredposition and orientation data for the region of the patient may beacquired using the substrate 10 and the associated sensor elements 16and the data may be automatically registered with concurrently orpreviously acquired image data without the use of anatomical or fiducialmarkers. In this way, the surgical procedure may be performed or guidedbased upon the dynamically referenced visual representation.

For example, referring to FIG. 5, exemplary acts corresponding to oneimplementation of the present technique are provided. In theimplementation depicted in FIG. 5, the image data 122 is acquired (Block120) prior to the invasive procedure. As noted above, the image data 122may be acquired using one or more suitable imaging modalities, such asthree-dimensional fluoroscopy, CT, MRI, and so forth. In the depictedembodiment, the image data 122 is used to generate (Block 124) one ormore visual representations, such as images or volumes 126, of theinternal organ 24 (see FIG. 2) or region of interest.

The images or volumes 126 are segmented (Block 128) in the depictedimplementation to provide one or more segmented regions 130. Such asegmentation process typically identifies pixels or those portions of animage representing common structures, such as organs or tissues. Forexample, a segmentation a process may identify surfaces or boundariesdefining an organ or tissue (such as by changes in intensity or someother threshold criteria). In this way, all of those pixels representingrespective organs or tissues, portions of such organs or tissues, orregions proximate or connected to such organs or tissues may beidentified and distinguished from one another, allowing processing orevaluation of only the portions of an image associated with the organsor tissues of interest.

The images or volumes 126 may be segmented using known segmentationtechniques, such as intensity and/or volume thresholding, connectivityclustering, and so forth. In one embodiment, the segmentation allows theorgan, tissue or region of interest to be geometrically modeled. In anexemplary embodiment, the segmented region corresponds to the internalorgan 24 or other structure upon which the substrate 10 (see FIGS. 1 and2) will be placed for dynamic referencing. While the depicted actionsdescribe an embodiment in which images or volume 126 generated from theacquired image data 122 are segmented, in other embodiments thesegmentation may be performed on the image data 122 itself, with thesegmented image data being subsequently used to generate images orvolume of the internal organ 24 or region of interest. Based upon thesegmented image or volume of the internal organ, i.e., the segmentedregion 130, a model 134 of the region is generated (Block 132) whichgenerally corresponds to the internal organ 24 or other region ofinterest as determinable form the imaging process.

In some embodiments, the region model 134 may incorporate image dataacquired using more than one type of imaging modality. For example, insome embodiments, it may be desirable to use image data derived formboth an MRI system and an X-ray based imaging system, such as athree-dimensional fluoroscopy system. In such an embodiment, the signalsacquired by both system may be registered, as discussed below, such thatthe combined images and/or volumes 126, segmented region 130 and/orregion model 134 consists of or is representative of the imageinformation acquired by each imaging modality.

During the invasive procedure performed on the internal organ 24 (orother region of interest), the substrate 10 is placed (Block 140) on theinternal organ 24. As noted above, the substrate 10 includes at leastthree sensor elements 16. The sensor elements 16 generate respectivesignals (such as respective EM fields) which may be acquired (Block 142)or measured to derive position and/or orientation data 144 for eachrespective sensor element 16. The position and/or orientation data 144may be used to generate (Block 146) a reference model 148 representingthe surface of the internal organ 24.

The reference model 148 derived from the position and/or orientationdata 144 is registered (block 150) with the region model 134 generatedusing the imaging process. In an exemplary embodiment, the registrationof the reference model 148 and the region model 134 is accomplishedautomatically, such as using iterative closest point techniques. In thismanner, the sensor elements 16 of the substrate 10 are automaticallyregistered to the surface of the internal organ 24, such as the liver.As will be appreciated, the more sensor elements 16 present on thesubstrate 10, the more robust and accurate the automatic registrationprocess will be. Further, in embodiments in which the sensor elements 16are integrated on a substrate 10 that conforms to the internal organ 24,soft tissue deformation of the internal organ 24 may be captured by thesensor elements 16 as the substrate 10 conforms to accommodate motion ordeformation of the internal organ 24. In such an embodiment, adeformable registration process may be employed to find correspondencesbetween the sensor elements 16 on the moving or deforming internal organ24 and the corresponding images or volumes. In other words, a deformableregistration process may be employed to allow the sensor elements 16 tobe registered to the corresponding images or volumes even though theinternal organ 24 may have moved or may be shaped slightly differentlybetween the time the image data 122 was acquired and the time theposition and/or orientation data 144 was acquired.

An image-guided invasive procedure may be performed using the registeredreference model 148 (based on the position and/or orientation data) andregion model 134 (based on the image data). In particular, once thepreviously acquired image-based information or model is registered tothe measured position and/or orientation data, changes in the positionand/or orientation data can be used to visually indicate changes to theimage-based model. In other words, a displayed image of the internalorgan 24 may be updated, modified, altered, or otherwise, changed, basedon the most current position and/or orientation data obtained from thesensor elements 16 placed on the internal organ 24. In this way, eventhough no imaging processes are occurring during the operation, thepreviously acquired image data can be updated and manipulated to providean accurate and current representation of the internal organ (or otherinternal region) undergoing the procedure.

Based on this registration between the region model 134 (derived theimage data) and reference model 148 (derived from the sensor elementdata), a surgical instrument may be tracked (Block 152) during aninvasive procedure, such as a surgical open or laparoscopic procedure.Examples of such surgical instruments that may be tracked include biopsyneedles, catheters, ablation needles, forceps, and so forth. Typicallythe surgical instrument being tracked also includes a sensor element 16,such as an EM sensor, so that position and/or orientation informationfor the surgical instrument is also acquired, thereby allowing theposition of the surgical instrument to be displayed in conjunction withthe registered image of the moving and/or deformed internal organ 24. Inthis manner, a system such as those described herein, may display to auser in real-time or substantially real-time the location of thesurgical device relative to the moving and/or deformed internal organ24.

While the preceding described an implementation in which the imagingprocedure is performed prior to the surgical procedure, in otherimplementations the imaging procedure is performed concurrently with thesurgical procedure. For example, referring to FIG. 6, acts associatedwith a further exemplary embodiment of the present technique aredepicted. In this embodiment, the sensor elements 16 integrated on asubstrate 10 are placed on the internal organ 24 of interest, such asvia an open surgical or laparoscopic procedure. Position and/ororientation data 158 is acquired (Block 156) for the sensor elements 16placed on the surface of the internal organ 24. For example, inembodiments where the sensor elements 16 generate EM signals or fields,these signals or fields can be detected and/or measured, such as usingone or more antenna arrays as described above, to derive a positionand/or orientation for each respective sensor element 16.

In the depicted embodiment, image data 122 is acquired (Block 120) andis used to generate (Block 124) one or more images and/or volumes 126.Some or all of the sensor elements 16 are located (Block 162) in theimages and/or volumes 126 such that the position data 164 for therespective sensor elements 16 is obtained with respect to theimages/volumes 126. In an exemplary embodiment, the sensor elements 16are automatically located in the images/volumes 126. For example, thesensor elements 16 may be automatically located using image processingtechniques such as intensity and/or volume thresholding, connectivityclustering, template matching, and so forth. In addition, in someembodiments, the positions of the sensor elements 16 are known withrespect to one another based on the measured signals or fields generatedby the sensor elements 16. This sensor derived position data 158 may beused to find the sensor elements 16 in the images and/or volumes 126.

Once some or all of the sensor elements 16 are identified in the imagesand/or volumes, the positions 164 of the sensor elements 16 located inthe images and/or volumes may be matched (Block 166) to thecorresponding sensor element locations as determined from the sensorposition data 158. In other words, the sensor elements 16 located in theimages and/or volumes are matched with the corresponding sensor elementssignals and/or fields generated by the sensor elements 16. In oneembodiment, this may be facilitated by using a non-symmetric pattern ofsensor elements 16 on the substrate 10. Alternatively, a sufficientlylarge number (i.e., four or more) of sensor elements 16 may be providedin one embodiment such that all possible matches may be permuted and thematch generating the smallest registration error is selected as thecorrect match or correspondence.

Based on the established or possible correspondences, the sensor elementpositions derived using the sensor data and the imaging data areregistered (Block 168). As noted above, in some embodiments, theregistration and the establishment of the correspondences may actuallydepend on one another, i.e., the registration errors associated withdifferent possible matches may be used to select the correctcorrespondence. In one embodiment the centroid of each sensor element 16as determined in the images and/or volumes is registered to thecorresponding sensor element signal in the position data derived fromthe sensor elements 16. In certain implementations the registration canbe accomplished using iterative optimization techniques or a closed formsolution. As noted above, in certain embodiments, to obtain a uniqueregistration it is generally desired that the three or more sensorelements not lie on or near a straight line.

Once the sensor elements 16 are registered in both the sensor space(such as EM space) and the image space, the interventional procedure maybe performed using the dynamic tracking of the internal organ based uponthe signals from the sensor elements 16. For example, no further imagingmay be performed or the image data may be updated only sporadically,with other updates to the images used in the interventional procedurebeing based upon the continuous, substantially real-time tracking of thesensor elements 16. In this way, even though imaging does not occur oroccurs only sporadically during the operation, the displayed images canbe updated and manipulated to provide an accurate and currentrepresentation of the internal organ 24 (or other internal region)undergoing the procedure.

In one implementation a surgical instrument may be tracked (Block 152)during an invasive procedure, such as a surgical open or laparoscopicprocedure, using images updated based upon the position data derivedform the sensor elements and the registration of these signals with theimage and/or volumes 126. Examples of such surgical instruments that maybe tracked include biopsy needles, catheters, ablation needles, forceps,and so forth. Typically the surgical instrument being tracked alsoincludes a sensor element 16, such as an EM sensor, so that positionand/or orientation information for the surgical instrument is alsoacquired, thereby allowing the position of the surgical instrument to bedisplayed in conjunction with the image updated using the position datafor the sensor elements 16. In this manner, a system such as thosedescribed herein, may display to a user in real-time or substantiallyreal-time the location of the surgical instrument relative to the movingand/or deformed internal organ 24.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A method for tracking dynamic motion of an organ comprising the actsof: powering three or more sensor components integrated on a substrateplaced on an internal organ using a power supply electrically connectedto the three or more sensor components; generating a first set ofposition data for the three or more sensor components, wherein the firstset of position data is based on signals or fields generated or detectedby the sensor components; generating a second set of position data forthe three or more sensor components based on an identification of thethree or more sensor components in one or more radiological images orvolumetric representations of the internal organ; identifyingcorresponding sensor components in the first set of position data andthe second set of position data; and registering the first set ofposition data with the one or more radiological images or volumetricrepresentations based on the identification of corresponding sensorcomponents in the first set of position data and the second set ofposition data.
 2. The method of claim 1 further comprising generatingthe one or more images or volumetric representations based on image dataacquired using at least one of computed tomography, magnetic resonanceimaging, ultrasound, or three-dimensional fluoroscopy.
 3. The method ofclaim 1 wherein at least one of generating the first set of positiondata, generating the second set of position data, identifyingcorresponding sensor components, or registering the first set ofposition data with the one or more images or volumetric representationsis performed automatically.
 4. The method of claim 1 further comprisingtracking a surgical instrument using the registered first set ofposition data and the one or more images or volumetric representations.5. A method for tracking dynamic motion of an organ comprising the actsof: powering one or more sensor components provided on a substrateplaced on an internal organ using a power supply electrically connectedto the one or more sensor components; generating position andorientation data for the one or more sensor components, wherein theposition and orientation data is based on signals or fields generated bythe sensor components; generating a shape model of the substrate basedon the position and orientation data; segmenting a region of interest inone or more radiological images or volumetric representations, whereinthe region of interest comprises at least one of the internal organ, aportion of the internal organ, or a region proximate or connected to theinternal organ; generating a shape model of the region of interest basedon the segmentation; and registering the shape model of the substrateand the shape model of the region of interest.
 6. The method of claim 5further comprising generating the one or more images or volumetricrepresentations based on image data acquired using at least one ofcomputed tomography, magnetic resonance imaging, ultrasound, orthree-dimensional fluoroscopy.
 7. The method of claim 5 wherein at leastone of generating the position and orientation data, generating theshape model of the substrate, segmenting the region of interest,generating the shape model of the region of interest, or registering theshape model of the substrate and the shape model of the region ofinterest is performed automatically.
 8. The method of claim 5 furthercomprising tracking a surgical instrument using the registered shapemodel of the substrate and shape model of the region of interest.
 9. Themethod of claim 5, further comprising placing the substrate on theinternal organ via a surgical open or laparoscopic technique.